How will the ancestral property divided if one legal heir has died

Hi, My grandmother has an ancestral property, which is to be divided amongst her 4 children - 2 sons, and 2 daughters. One son passed away last year, leaving behind a son from his first marriage, and a wife from his second marriage. The second wife has 2 kids from her first marriage, who are not related by blood to the grandmother. So, on death of the son, how will the property be divided amongst the heirs? I understand that the son's share will go to the grandson and to his widow from the second marriage. Do her children also become a part of the succession certificate? Please answer this query. Thanks